In networks for mobile telecommunications, as regards dedicated channels, radio resources may be assigned exclusively to one user terminal for the entire time that the user is allocated the channel, regardless of whether the user terminal is using the channel or not. This is illustrated in FIG. 1.
It is known that sharing dedicated channels between user terminals enhances efficiency. This approach involves the use of an inactivity timer, whereby the network monitors the activity of all the packet-switched users, and when the network detects that there is no data activity (i.e., data communications to or from a particular user), the inactivity timer for that user terminal is started. Once the timer has been started, if the network detects activity for that particular user terminal, the timer is reset, to be re-started when the activity for that user terminal again ceases. If there is no activity for that user terminal until the expiry of the timer, the user terminal relinquishes its radio resources, though the connection with the network is still maintained. When this user has more data to send, the network allocates to the user terminal new radio resources. This approach is illustrated in FIG. 2. Using this approach, the radio resources freed by the use of the inactivity timer can then be utilised by other users. FIG. 3 is a diagram showing this.
In applications where the user traffic does not follow a predetermined traffic pattern, the user changes between the ‘active’ and ‘inactive’ states in a non-deterministic fashion. This is because the time interval between successive data activity periods varies greatly during a call.
Signalling may be required for the network to transition the user between the ‘active’ and ‘inactive’ states, with consequential use of base station transmit power. Part of the signalling to make the users change between the ‘active’ and ‘inactive’ states is performed on a (shared) signalling channel. As a signalling channel has no power control (or very crude power control), its use requires a significant amount of base station transmit power.
On the one hand, if the value of the inactivity timer is large, the transitions between the ‘active’ and ‘inactive’ states do not occur as frequently, and as a consequence, less signalling, and consequential power usage for signalling, is required; however, there is, of course, a longer delay before resources are reallocated to another user, which can be undesirable.
On the other hand for a small inactivity timer value, the user transitions back and forth between the ‘active’ and ‘inactive’ states frequently. Frequent signalling is involved to change between the two states during which a large amount of base station transmit power is required. Furthermore, there are user terminals that require less base station transmit power in the ‘active’ state than for signalling. With frequent signalling, the overall base station transmit power allocated for those users is higher, as illustrated in FIG. 4. This holds true for any network where the base station transmit power required for signalling is higher than the base station transmit power required by the corresponding ‘active’ state.